1. Field of the Invention
The invention relates to a hinge structure and, more particularly, to a cover hinge structure having self-protection function.
2. Description of the Related Art
As shown in FIG. 5, a conventional hinge 51, which is made of metal or plastic materials, connects a cover 52 with a body 53 by fixing the two leaves of hinge 51 onto the cover and body with screws 54. This prior hinge structure is quite durable; however, additional fixing members (not shown) for supporting the screws 54 are necessary when assembling the hinge 51, cover 52, and body 53. In addition, the hinge 51 is made separately from the cover 52 and body 53, thereby increasing the fabricating cost and complicating the assembling procedure. Besides, the screws and the additional fixing members also increase the size of a device.
Therefore, a simple hinge structure 60 shown in FIG. 6 is widely used for taking the place of the prior hinge 51. A hinge structure 60 includes a cylindrical hinge pin 61 integrated with a body 65 and a hook 62 integrated with a cover 64 (see FIG. 7A). The pin 61 is introduced into a hole 63 located at one end of the hook 62, thereby the hook 62 rotates around the pin 61 freely. When the cover 64 is lifted, the hook 62 rotates about the pin 61, thereby the cover 64 moves around the body 65. FIG. 7B shows a transformation of the hinge structure 60 shown in FIG. 7A, wherein a pin 61 is fixed on a hook 62 and a hole 63 is located at the body 65.
When assembling the hinge structure 60, the hook 62 is pulled outward slightly to let the pin 61 slip into the hole 63. After the hook 62 is released, the pin 61 is restricted within the hole 63 with the resilience of the hook 62. The hinge structure 60 is advanced in that it can be easily made with low cost and be quickly assembled. However, if the cover 64 is lifted up with great force or is continuously rotated after the pivotal motion of the cover 64 is restricted by the body 65, the pin 61 breaks at its base end. Besides, the pin 61 tends to escape from hole 63 easily.
Therefore, hinge pins with two base ends are provided to make the hinge structure more durable. Referring to FIG. 8A, a prior hinge structure 80 includes a pin 81 and a hook 82. The cylindrical hinge pin 81 connects to a body 85 at its both ends, while the hook 82 connects to the cover 84 at its base end. An engaging groove 83 forms at another end of the hook 82. As seen in FIG. 8A, an opening 86 for assembling of hinge structure 80 forms under the engaging groove 83. The width of the opening 86 is slightly larger then the diameter of the pin 81, thereby the pin 81 enters the engaging groove 83 easily by way of the opening 86 when assembling the pin 81 with the hook 82. Because of the weight of the cover 84, the hook 82 is forced downward during rotating of the cover 84, and the contact region for the pin 81 and the hook 82 is restricted between points P, Q, and R. Accordingly, undesired detachment of the pin 81 from the engaging groove 83 is prevented.
Referring to FIG. 8B, when the body 85 stops pivotal motion of the cover 84, that is, the cover 84 is lifted to the limit, since rotating direction a of the cover 84 differs from the opening direction of the opening 86 of the engaging groove 83, while the contact point A of the pin 81 and hook 82 is away from the opening 86, the pin 81 will not escape from the engaging groove 83. In addition, the conformation of the hook 82 is specially designed so that the pin 81 and the hook 82 can be detached only when they are adjusted to a particular angular range. Besides, the width of the opening 86 can be slightly smaller than the diameter of the pin 81 to avoid detachment of the pin 81 and the hook 82.
Another prior hinge structure 90 consists of a pin 91 and a hook 92, as seen in FIG. 9A. The base end of the hook 92 connects to a cover 94 and the engaging end of the hook 92 includes an extruding front jaw 98 and an extruding rear jaw 99. The front jaw 98 and rear jaw 99 are of the same length, while the opposite surfaces of both jaws are curved to jointly form a substantially C-shaped engaging groove 93 having an internal diameter substantially the same as the diameter of the pin 91. Distance between the extruding ends of the front jaw 98 and the rear jaw 99 is smaller than the diameter of the pin 91, thereby forming an opening 96 narrower than the pin 91. The hook 92 further includes an resilient slit 97 extending from the engaging groove 93 toward the base end of the hook 92. When assembling the pin 91 with the hook 92, the opening 96 is directed toward the pin 91 and the hook 92 is pressed against the pin 91. The pin 91 applies reaction forces onto the extruding ends of the front jaw 98 and the rear jaw 99, thereby pressing the front jaw 98 and the rear jaw 99 outwardly. Part of the hook 92 around the resilient slit 97 deforms outwardly, too, and the width of the opening 96 increases gradually. As the width of the opening 96 equals to the diameter of the pin 91 when the reaction forces coming from the pin 91 reaches a certain value (that is, the action force from the hook 92 to the pin 91 reaches a certain value), the pin 91 slips into the engaging groove 93. The pin 91 is held by the front jaw 98 and the rear jaw 99 since the internal diameter of the engaging groove 93 is substantially the same as the diameter of the pin 91. Because the width of the opening 96 is narrower then the diameter of the pin 91 and the hook 92 is elastic, the pin 91 stays within the engaging groove 93 during pivotal motion of the cover 94. Besides, as described above, the hook 92 is forced downward during rotating of the cover 94 because of the weight of the cover 94, and the contact region for the pin 91 and the hook 92 is restricted at the upper portion of the inner surface of the engaging groove 93. Accordingly, undesired detachment of the cover 94 from the body 95 is prevented.
However, the aforementioned hinge structures 80 and 90 may easily break down when the body stops the pivotal motion of the cover, that is, the cover is lifted to the limit. Referring now to FIG. 8B, if the cover 84 is forced to rotate after the cover 84 contacts a point B of the body 85, the rotating direction of the cover 84 points to direction a, the reaction force applied from the pin 81 to the hook 82 points to direction c and acts on a point A away from the opening 86. Thus, the hook 82 deforms. At this moment, if the applied force is large enough to make the deformation of the hook 82 exceed its elastic limit, the hook 82 is damaged or even breaks down.
On the other hand, if the hook 82 contacts point B of the body 85 after the cover 84 is lifted to the limit, as shown in FIG. 8C, the rotating direction of the cover 84 points to direction a, the reaction force applied from the pin 81 to the hook 82 points to direction e, and the opening direction of the opening 86 points to direction b. The direction b and direction e are substantially parallel; nevertheless, the reaction force applied from the pin 81 to the hook 82 acts on point C that is away from the opening 86. Therefore, undesired detachment of the pin 81 and the hook 82 is prevented. However, for the conventional plastic materials used for making the case of a device (e.g., ABS or the like), the pin 81 does not escape from the groove 83 if deformation of the hook 82 is under its elastic limit even though the reaction forces from the pin 81 deforms the hook 82 (FIG. 8D). Similarly, if the applied force is large enough to make the deformation of the hook 82 exceed its elastic limit, the hook 82 is damaged or even breaks down.
For the hinge structure 90, the hook 92 contacts a point B of the body 95 when the cover 94 is lifted to the limit, as seen in FIG. 9B. The rotating direction of the cover 94 points to direction a, the reaction force applied from the pin 91 to the hook 92 points to direction e and acts on point C of the front jaw 98. Thus, the hook 92 deforms. If the applied force is large enough to make the deformation of the hook 92 exceed its elastic limit, the hook 92 is damaged or even breaks down. In order to make the hinge structure 90 more durable, the front jaw 98 is thickened to increase its tolerance to the reaction force. However, damage or breaking down of the hinge structure remains unavoidable.